Corrosion protection for lubricants

ABSTRACT

The present invention relates to compositions comprising at least one triazole-containing species and at least one thiadiazole-containing species, which in embodiments are suitable for manual transmission oils.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Provisional Application No. 60/673,858 filed Apr. 22, 2005, the disclosure of which is incorporated by reference.

FIELD OF THE INVENTION

The invention relates to lubricating compositions and other functional fluids. The compositions comprise at least one triazole-containing species and at least one thiadiazole-containing species. In preferred lubricating compositions, at least one extreme pressure (EP) component and at least one phosphorus-containing antiwear component are also present. In preferred embodiments the compositions are particularly useful in manual transmission oils.

BACKGROUND OF THE INVENTION

Emerging industry requirements for manual transmission fluids in the areas of micropitting and corrosion protection have created a need for new lubricant compositions. In order to meet these requirements, new additive systems suitable for blending with appropriate base stocks are needed. It is desirable that these new requirements be met without detracting from the positive properties of current lubricant compositions, particularly properties relating to oxidative and thermal stability, load carrying/antiwear performance, seal compatibility, and the like.

Manual transmission fluids, otherwise known as manual transmission oils or MTOs, are typically used in automobiles, light trucks, and heavy duty trucks. The torque from the engine is transferred directly to the driveline through mechanical clutch and speed increasing/reducing gears, e.g., spur gears. The fluids that lubricate such gears need to possess a variety of conventional features: extreme pressure (EP) performance for load carrying, antiwear performance, yellow metal corrosion protection, rust inhibition, foam suppression, thermal and oxidative stability, cleanliness, seal compatibility, among others. EP components, typically based on sulfur (S) and/or boron (B), and antiwear components, typically based on phosphorus (P), are therefore often part of lubricant compositions. Examples of such additives are disclosed in numerous patents, such as U.S. Pat. Nos. 4,900,460; 5,500,140; 5,547,596; 5,691,283; 5,756,429; 6,046,144; 6,605,572; U.S. Patent Application No. 2003/0176299; WO 03/104620; EP 1422287; EP 391653; EP 531000; EP 450208; and EP 531585.

However, corrosion may be seen in the field with the use of S, P-based lubricants, particularly when copper-containing components, e.g. coolers, are employed. Consequently, OEMs are issuing specifications which make it difficult for formulators to use S, P-containing additives. Therefore, many have stopped using S, P-containing additive systems because of corrosion issues.

New demands with respect to micropitting, corrosion protection and durability are placing severe demands even on MTOs not using S, P chemistry. Original Equipment Manufacturers (OEMs) are requiring proof of performance in new micropitting tests and extended corrosion tests, while also expecting to see maintained or improved EP and antiwear protection over longer periods of time. Consequently, extended drain intervals, improved durability, and enhanced corrosion and micropitting protection are key features required of new transmission fluids. Conventional S, P packages struggle to meet a satisfactory level of performance.

Given the enormous number of ingredients proposed for additive packages, it is a formidable task to find the right combination capable of meeting the number of new requirements desired in driveline fluids such as MTOs while maintaining traditional performance standards in other areas. Numerous attempts have been made to improve corrosion problems in formulations based on S, P chemistry.

U.S. Pat. No. 4,511,481 discloses industrial lubricants stabilized with a triazole adduct of amine phosphates, providing oxidation stability, antiwear, and rust preventative performance.

Dimercaptothiadiazole derivatives, such as 2,5-dimercapto-1,3,4-thiadiazole, disodium 2,5-dimercaptothiadiazole, and 2,5-bis(t-nonyl-dithio) thiadiazole, are known for their antioxidancy, anticorrosion, and metal passivation properties as disclosed in, for instance, U.S. Pat. Nos. 4,382,869, 4,661,273, 4,678, 592 and 4,584,114.

Furthermore, U.S. Pat. No. 5,186,850 discloses that the incorporation of the heterocyclic dimercaptothiadiazole functionality into succinimide structures provides ashless dispersants with multifunctional antiwear, antioxidant and corrosion inhibitor properties in lubricant compositions.

U.S. Pat. No. 5,205,945 describes a multifunctional antioxidant, antiwear, and dispersancy additive for fuels and lubricants is a reaction product of a thiol-substituted diazole, such as aminomercaptothiadiazole (AMTD) or dimercaptothiadiazole (DMTD), an aldehyde and a hydrocarbon-substituted succinimide dimer.

U.S. Pat. No. 5,538,652 is directed to combinations of dimercaptothiadiazole-mercaptan coupled dithio compounds with amines which have proven to be highly effective multifunctional antiwear/extreme pressure additives for lubricants and fuels.

U.S. Pat. No. 6,180,575 discloses a lubricating oil having additives comprising an adduct of a substituted triazole with an amine phosphate in order to balance anti-wear and anti-rust properties. See also WO 2000/08119.

The present inventors have discovered a composition which, in preferred embodiments in combination with suitable basestocks, is able to meet the newest industrial requirements for MTOs without sacrificing the positive attributes of currently available commercial products.

SUMMARY OF THE INVENTION

The lubricant composition of the invention comprises a combination of at least one triazole-containing species and at least one species selected from a thiadiazole-containing species. In embodiments the invention provides improved corrosion protection for manual transmissions.

In other embodiments, the composition will also include one or more ingredients selected from: (a) at least one extreme pressure (EP) component selected from sulfur-containing component; and (b) at least one phosphorus-containing antiwear component. In embodiments comprising at least one sulfur-containing EP component, a preferred composition is characterized by a mass ratio of sulfur to that of the triazole-containing species of less than or equal to 150:1.

In even more preferred embodiments, lubricant compositions comprising alkyl polysulfides and alkyl phosphate esters, in combination with a triazole-containing corrosion inhibitor, such as tolyl triazole and dimercaptothiadizole, have been found particularly effective in avoiding corrosion of copper.

In other embodiments the lubricant composition of the invention will comprise a dispersant and/or a rust inhibitor, and optionally other ingredients.

The invention is also directed, in preferred embodiments, to formulated MTOs comprising at least one basestock selected from API Group I through V basestocks and an additive system. In more preferred embodiments, the invention is directed to formulated MTOs comprising at least one API Group IV and/or Group V basestock and an additive system.

It is an object of the invention to provide lubricating oils containing high levels of sulfur that do not significantly corrode yellow metals.

It is another object of the invention to provide a lubricant formulation based on S, P chemistry that provides high temperature copper corrosion resistance.

It is still another object of the invention to provide improvements in the area of micropitting and load carrying/antiwear protection.

These and other objects, features, and advantages will become apparent as reference is made to the following detailed description, preferred embodiments, examples, and appended claims.

DETAILED DESCRIPTION

According to the invention, a lubricant composition is provided comprising a combination of at least one triazole, triazole derivative, or salt thereof, referred to herein as “triazole-containing species”, and at least one species selected from a thiadiazole-containing species.

In embodiments, the lubricant composition will also include ingredients selected from: at least one extreme pressure (EP) component selected from sulfur-containing and/or boron-containing species; and at least one phosphorus-containing antiwear component.

In embodiments comprising at least one sulfur-containing EP component, a preferred lubricant composition is characterized by a mass ratio of sulfur to triazole-containing species of less than or equal to 150:1.

Additional embodiments are described herein below.

Critical ingredients are selected from the following materials.

A. Triazole-Containing Species.

A key ingredient in the lubricant composition according to the invention is a triazole, triazole derivative, or salt thereof, referred to herein as “triazole-containing species”. Preferred triazole-containing species include those known in the art per se as corrosion-inhibiting agents. While the exact amount used is not critical, an effective amount should be used. This may be determined by one of ordinary skill in the art in possession of the present disclosure. Typically, the amount of triazole and/or derivative used will depend on the level of sulfur-containing EP agent(s). Appropriate amounts may be determined by one of ordinary skill in the art in possession of the present disclosure without more than routine experimentation.

Triazoles, e.g., 1,2,4-triazole, 1,2,3-triazoles, and their derivatives and salts, several of which are commercially available (from, for example, Aldrich Chemicals) have been found to be important for reducing bearing wear in industrial gear oils and preventing corrosion in manual transmissions. Since triazole itself is difficult to solubilize in oil or in an additive mix, it advantageously can be derivatized. The derivatives provide a means for making the triazole group more soluble in oil but retain its corrosion and wear reducing properties. Some specific examples of derivatives include: benzotriazole, tolytriazole, octyltriazole, decyltriazole, dodecyltriazole, 2-mercaptobenzotriazole.

Alkyl and aryl derivatives of triazoles are preferred. Most preferred is the tolyltriazole.

Any species containing the triazole species is useful in the composition according to the invention. The prior art described in the Background section above lists numerous triazole-containing species useful in the present invention. In addition, any of the triazoles mentioned above, including those set forth in the prior art, may also be present as carboxylic acid salt, e.g the salt of a fatty acid, like oleic acid or the salt of polybutenyl succinic acid. Adducts containing triazole species may also be used, e.g., amide derivatives prepared by reacting a carboxylic acid with the amine of the triazole, are also included in the scope of this invention.

Additionally, the triazole can also be present in the form of a salt of one of the phosphorus acid species described below. A particularly preferred embodiment of the invention is the complex of the triazole derivative with an alkyl or aryl acid phosphate.

B. Thiadiazoles

At least one thiadiazole-containing species must be present in a composition according to the present invention. While the exact amount used is not critical, an effective amount should be used. This may be determined by one of ordinary skill in the art in possession of the present disclosure without more than routine experimentation.

Preferred thiadiazoles include dimercaptothiadiazole (DMTD) and its alkylated derivatives, known per se as a class of copper corrosion inhibitors. Specific examples of the thiadiazoles include 2-mercapto-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazoles, 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazoles, 2,5-bis-(hydrocarbylthio)-1,3,4-thiadiazoles, and 2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazoles. The preferred compounds are the 1,3,4 thiadiazoles, especially the 2-hydrocarbyldithio-5-mercapto-1,3,4-dithiadiazoles and the 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazole. Several of these are commercially available, e.g. Afton Hitec™ 4313 and Mobilad™ C-610.

Other suitable inhibitors of copper corrosion that may be used along with the required thiadiazoles and the triazoles include thiazoles, imidazolines, ethoxylated phenols and alcohols, and the like. However, the present inventors have discovered that the critical ingredients to assist in meeting at least one object of the invention, at least in preferred formulated lubricant compositions, is the presence of the triazole-containing species in combination with the thiadiazole-containing species.

These critical species, as well as any optional ingredients, may be delivered separately or in combination as an additive package, with or without additional components, to a basestock, to make a lubricant composition or other functional fluid.

Preferred optional ingredients in a formulated lubricant composition according to the invention, include at least one of the following species set forth in C., D. or E., below. Typically mixtures of at least one ingredient selected from each of the following groups will be included.

C. Extreme Pressure Agents

Extreme pressure (EP) agents useful in the composition according to the invention include known sulfur-containing and boron-containing EP agents. Sulfur-containing EP agents are preferred.

Sulfurized olefins are known per se to be useful to provide protection against high pressure, metal-to-metal contacts in industrial and automotive gear oils. However, the presence of sulfurized olefins for this purpose must be balanced against the drawback that the presence of sulfur lowers thermal stability, increases the aggression against certain seal materials, and increases corrosivity toward copper-containing alloys.

There is no particular restriction on the sulfur-containing extreme pressure additive that can be used in the additive package of the invention. Sulfur-containing components useful in this regard include sulfurized olefins, dialkyl polysulfides, diarylpolysulfides, sulfurized fats and oils, sulfurized fatty acid esters, trithiones, sulfurized oligomers of C2-C8 monoolefins, thiophosphoric acid compounds, sulfurized terpenes, thiocarbamate compounds, thiocarbonate compounds, sulfoxides, and thiol sulfinates. Mixtures of sulfur-containing EP components may be used.

The preferred sulfur-containing EP components are selected from sulfurized oligomers of C2-C8 monoolefins, olefin sulfides and dialkyl and diaryl polysulfides.

A very large number of sulfurized olefins suitable for use as extreme pressure agents are detailed in the prior art. See, for instance, U.S. Pat. No. 6,844,300 and references cited therein.

The more preferred extreme pressure agents are oligomeric olefin sulfides and dialkyl polysulfides. Oligomeric olefin sulfides are prepared via the reaction of sulfuryl monochloride with an olefin, e.g. isobutylene, to create an oligomeric olefin sulfide compound. The drawback to these materials is the residual chlorine, which the process leaves behind, but this can be reduced by various treatments. U.S. Pat. Nos. 2,249,312; 2,708,199; 3,471,404; 4,204,969; 4,563,302; 4,954,274; and 4,966,720 and European Patent No. 737,674A2 and British Patent No. 1,308,894 describe the preparation of these sulfurized olefins.

Dialkyl polysulfides are prepared via a high pressure sulfurization procedure such as described in U.S. Pat. Nos. 4,119,550; 4,119,549; 4,344,854; 5,135,670; and 5,338,468. These may be prepared, for instance, by the reaction of sulfur, an olefin, and hydrogen sulfide, which may be provided in situ or added from an external source. The preferred method for the purpose of providing an extreme pressure agent for use in the additive package of the present invention involves generating the hydrogen sulfide in situ. In a more preferred embodiment, hydrogen sulfide is formed in the reactor from sodium hydrogen sulfide and consumed within the reactor.

In a more preferred embodiment, the high pressure sulfurized olefin is prepared by reacting an olefin, preferably isobutylene, with molten sulfur in predetermined quantities in the presence of aqueous sodium hydrogen sulfide under high pressure conditions. Commercially available high pressure sulfurized isobutylene (HPSIB) include Mobilad™ C-170 and Mobilad™ C-175. The synthesis of these preferred HPSIBs have been described in the prior art, such as U.S. Pat. No. 5,135,670 and WO 92/03524, and elsewhere.

While not critical to the characterization of the present invention, in a preferred embodiment, the weight percent of sulfur contributed by additives in any form in the lubricant is 0.1-3 wt %, more preferably 0.2-2.0 wt %.

Boron-containing EP agents are also per se known in the art. However, boron-containing EP agents appear to have deficiencies in the area of hydrolytic stability, so if a gear box is exposed to water, the boron-containing EP agents may be hydrolyzed and lose their effectiveness as EP components. Also, the EP properties may be less relative to some sulfurized olefins, and therefore for certain driveline applications, sulfurized olefins may be added along with the boron-containing additives. In manual transmissions, it is possible that boron-containing EP additives may be adequate, if there is no water present. In embodiments, a mixture of boron-containing and sulfurized olefins may be used as EP components. However, in preferred embodiments, the composition according to the present invention does not use an extreme pressure ingredient containing boron.

D. Phosphorus-Containing Antiwear Agents

There is no particular restriction on the type of phosphorus containing compounds. Oil soluble antiwear and/or extreme pressure agents that are typically used in industrial gear and drivelines fluids are for the most part partially or full esterified acids of phosphorus. All of these are considered for this invention. They can include the following: acid phosphates, hydrogen phosphites, phosphites, phosphates, phosphonates, phosphinates, and phosphoroamidates. They can also include the sulfur analogs of all of these. Examples include mono, di and trihydrocarbyl phosphites; mono, di, and trihydrocarbyl phosphates; mono, di, and trihydrocarbyl mono, di, tri, tetrathiophosphates; mono, di, trihydrocarbyl mono, di, tri, tetrathiophosphites; various hydrocarbyl phosphonates and thiophosphonates; various hydrocarbyl phosphonites and thiophosphonites, etc. Specific examples include tricresyl phosphate, tributylphosphite, triphenyl phosphite, di-2-ethylhexyl phosphate, di-isooctyl phosphate, diisobutylhydrogen phosphite, diisopropyl dithiophosphate, diphenyl phosphate, etc. All of the amine salts that can be formed with these materials are also included and the types of amines that can be used are described in a later section. The preferred embodiments are the mono and di-alkyl acid phosphates, e.g. mono and di-2-ethylhexyl phosphoric acid and mono and diaryl phosphates, e.g. Irgalube 349 from Ciba, and their amine salts.

While not critical to the characterization of the present invention, in a preferred embodiment the level of elemental phosphorus in the formulated lubricant composition according to the invention is about 0.01-1 wt %, more preferably 0.03-0.5 wt %.

E. Other Optional Ingredients

Other ingredients such rust inhibitors, dispersants and/or cleanliness agents, antioxidants, defoamants, additional metal corrosion prevention agents (e.g. copper passivators), friction modifiers, seal swell agents, pour point depressants, diluents, and the like, may be present to provide the required oil attributes. As with the other optional ingedients listed in C. and D., above, these optional ingredients are part of a fully formulated lubricant or other functional fluid, or a combination thereof. Again, the effective amount of these optional ingredients may be determined by one of ordinary skill in the art in possession of the present disclosure.

A preferred but optional additive is a rust inhibitor. Rust inhibitors may be any oil-soluble basic amine or combinations of amines. The amines can be primary, secondary, tertiary, acyclic or cyclic, mono or polyamines. They can also be heterocyclic. The amine-containing components can also contain other substituents, e.g. ether linkages or hydroxyl moieties. The preferred amines are generally aliphatic in nature. Some specific examples include: octylamine, decylamine, C10, C12, C14 and C16 tertiary alkyl primary amines (or combinations thereof), laurylamine, hexadecylamine, heptadecylamine, octadecylamine, decenylamine, dodecenylamine, palmitoylamine, oleylamine, linoleylamine, di-isoamylamine, di-octylamine, di-(2-ethylhexyl)amine, dilaurylamine, cyclohexylamine, 1,2-propylene amine, 1,3-propylenediamine, diethylene triamine, triethylene tetraamine, ethanolamine, triethanolamine, trioctylamine, pyridine, morpholine, 2-methylpiperazine, 1,2-bis(N-piperazinyl-ethane), tetraminooctadecene, triaminooctadecene, N-hexylaniline and the like. They may also be triazole or triazole derivatives which are described elsewhere as a necessary ingredient in a composition according to the present invention.

The most preferred amines for this invention to serve as rust inhibitors are oil-soluble aliphatic amines in which the aliphatic group is a tertiary alkyl group. Exemplary of such amines include Primene™ 81R and Primene™ JMT, commercially available from Rohmax.

It should be noted that in a formulated lubricant composition according to the invention, as would be recognized by one of skill in the art in possession of the present disclosure, amines combine with the acid phosphates to form salts, which are also effective as antirust and antiwear agents. The salts of the phosphates and amines may be formed prior to addition to the lubricant composition or they may be formed in situ after the acid phosphate and amine are added to the additive package or to the formulated lubricant.

Amides, imides, and imidazolines, oxazolidones, and other related nitrogen-containing species can also be present as rust inhibitors, friction modifiers, or to serve some other purpose. Some examples of these include the reaction products of dodecenylsuccinic anhydride (DDSA) and tetraethylene pentamine, the reaction products of oleic acid and tetraethylene pentamine, the reaction products of diethylene triamine and DDSA, the reaction products of triethanolamine and nonanoic acid and the like.

A preferred but optional additive is at least one dispersant and/or cleanliness agent. Dispersants serve inter alia to keep sludge and varnish particles from coating on the gear surfaces. Numerous such agents are per se known in the art. There are no particular restrictions on the type to be used. They may be used singly or in combinations. They may be borated, partially borated or unborated. Typical examples of nitrogen-containing dispersants include alkylsuccinimides, alkenylsuccinimides, boron-containing alkylsuccinimides, boron-containing alkenylsuccinimides, benzylamines compounds (Mannich bases), polybutenylamines, succinic acid ester compounds, and the like.

In preferred embodiment, nitrogen-containing dispersants are selected from alkylsuccinimides, alkenylsuccinimides, and the boron-containing analog of both of these. The especially preferred ashless dispersants for use in this invention are the products of reaction of a polyethylene polyamine, e.g. triethylene tetraamine pentaamine, with a hydrocarbon-substituted anhydride made by the reaction of a polyolefin, preferably 700-1400 and especially 800-1200 with an unsaturated polycarboxylic acid or anhydride, e.g. maleic anhydride. The ashless dispersants can be borated to form ashless boron-containing dispersants using suitable boron-containing compounds: boron acids, boron oxides, boron esters, and amine or ammonium salts of boron acids.

Another preferred but still optional ingredient in the composition according to the invention include an antioxidant to protect the composition and reduce the decomposition by oxygen, especially at elevated temperatures. Typical antioxidants include hindered phenolic antioxidants, secondary aromatic amine antioxidants, and sulfurized phenolic antioxidants. Specific examples include diphenylamines, alkylated diphenylamines, phenyl-alpha-napthylamines, and t-butylphenol derivatives, styryl phenol and its derivatives. Note that one of the most common classes of antioxidants are the nitrogen-containing antioxidants, e.g, aromatic amine antioxidants such as diphenylamines, alkylated diphenylamines, and phenyl-α-napthylamines.

Anti-foam agents are also a preferred but still optional ingredient, useful to prevent or reduce the formation of stable foam. Typical anti-foam agents include silicone or organic polymers such as acrylate polymers. Some specific examples of anti-foam agents include polymethylacrylate and polybutylacrylate. One such alkylacrylate polymeric defoamer, Mobilad C-402, is commercially available from ExxonMobil Chemical Company. As an alternative, the anti-foaming ingredient may be added to the finished lubricant rather than or in addition to adding it to the additive package. Additional antifoam compositions are described in “Foam Control Agent,” by Henry T. Kerner (Noyes Data Corporation, 1976, pp 125-162).

Other ingredients that may be included are detergents, both metal and non-metal-containing, seal swell agents, friction modifiers, anti-chatter agents, and the like.

While the formulated lubricant composition, including necessary ingredients and optional ingredients, has been set forth in detail above, it will be understood by one of ordinary skill in the art that typically the above ingredients will be blended into an additive package or add pack which the oil formulators will add to a basestock or other fluids, e.g., carrier, hydraulic fluid, solvent, etc.

Regarding the mass ratio of sulfur to triazole-containing species, while not critical to a composition according to the invention, in embodiments it is 150:1 or less and in preferred embodiments it is 100:1 or less and still more preferred embodiments, it is 75:1 or less. Again, while not critical to the description, provided effective amounts of the required triazole-containing species is present, in embodiments the lower limit of sulfur to triazole derivative will be about 10:1. It will be recognized that certain basestocks may contain appreciable amounts of sulfur-containing species and the amount of sulfur contributed by the basestock should not be included in the aforementioned ratio.

The additives may be combined in whole or in part into an additive package, or they may be added separately to the final lubricant composition or other functional fluid. The blending operations in any of these cases do not need to be complex. They may involve simply mixing together in suitable proportions all the appropriate components. Those who are skilled in the art would be familiar with suitable procedures and for formulating and blending additive concentrates and lubricant compositions. Generally speaking, the order of addition is not critical unless in order to control exotherms it is necessary to alter the order, which may be determined by one of skill in the art without more than routine experimentation. Without wishing to be overly pedantic, agitation with a mechanical stirrer is typically desirable to facilitate blending. Some practitioners may wish to apply heat while blending. Generally, heating the blend between 40° and 100° C. will be sufficient. Naturally, the temperatures should be chosen so as not to cause any unwanted chemical reactions or thermal degradation. Blending under an inert atmosphere may be beneficial. Blending the finished lubricants is equally as straightforward.

Base oils

Note that the terms basestock and base oil are used interchangeably herein. Fluids that can meet the criteria of base oil for lubricant and functional fluids are varied. They may fall into any of the well-known American Petroleum Institute (API) categories of Group I through Group V. The API defines Group I stocks as solvent-refined mineral oils. Group I stocks contain the most unsaturates and sulfur and have the lowest viscosity indices. Group I defines the bottom tier of lubricant performance. Group II and III stocks are high viscosity index and very high viscosity index base stocks, respectively. The Group III oils contain fewer unsaturates and sulfur than the Group II oils. With regard to certain characteristics, both Group II and Group III oils perform better than Group I oils, particularly in the area of thermal and oxidative stability.

Group IV stocks consist of polyalphaolefins, which are produced via the catalytic oligomerization of linear alphaolefins (LAOs), particularly LAOs selected from C5-C14 alphaolefins, preferably from 1-hexene to 1-tetradecene, more preferably from 1-octene to 1-dodecene, and mixtures thereof, with 1-decene being the preferred material, although oligomers of lower olefins such as ethylene and propylene, oligomers of ethylene/butene-1 and isobutylene/butene-1, and oligomers of ethylene with other higher olefins, as described in U.S. Pat. No. 4,956,122 and the patents referred to therein, and the like may also be used. PAOs offer superior volatility, thermal stability, and pour point characteristics to those base oils in Group I, II, and III.

Group V includes all the other base stocks not included in Groups I through IV. Group V base stocks includes the important group of base stocks based on or derived from esters. It also includes alkylated aromatics, polyinternal olefins (PIOs), polyalkylene glycols (PAGs), etc.

One of the great benefits of the present invention is that it is applicable to base oils fitting into any of the above five categories, API Groups I to V, as well as other materials. As used herein, whenever the terminology “Group . . . ” (followed by one or more of Roman Numerals I through V) is used, it refers to the API classification scheme set forth above.

Such additional but optional ingredients that may be beneficial in the final lubricant or functional fluid composition that are typically not classified in the art as “additive” per se but are included in this scope of this invention are pour point depressants, viscosity index modifiers, thickeners, e.g. polyisobutylene, and tackifiers.

The following examples are meant to illustrate the present invention in more detail and provide a comparison with other methods and the products produced therefrom. Numerous modifications and variations are possible and it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

Manual Transmission Oils (MTOs)

The additive-containing lubricant compositions described in the preceding sections are useful for manual transmission oil formulations.

Manual transmission fluids generally will possess the same set of features that many other lubricants need to have: extreme pressure/anti-wear performance, metal corrosion protection, frictional features, seal compatibility, cleanliness, thermal and oxidative stability, antioxidancy, foam control, pour point depression. In addition, current MTOs in North America need to have exceptional corrosion protection, which is difficult for S, P systems. New MTOs must also possess satisfactory protection against micropitting. To accomplish this, lubricant compositions were prepared containing the key ingredients: a triazole-containing derivative and a thiadiazole-containing derivative. In addition, the fluids contained an extreme pressure additive chosen from sulfurized isobutylene and a P-containing antiwear additive. PAO and ester were used as base oils. The fluid was tested against several of the key performance tests in the proposed Eaton PS 164 rev 7 specification, which is known in the art.

The following examples of lubricant compositions of the present invention show a significant improvement over conventional gear and transmission lubricants. A series of lubricant compositions were prepared using synthetic base stocks. The additives included in each composition are listed in Table 1 and include extreme pressure, antiwear, anti-corrosion, cleanliness, etc. agents. The three extreme pressure additives used differ in their sulfur content. The first contains a level of sulfur ranging from 47-52 wt %; the second from 45-49 wt %; the third from 41-46 wt %. The base stocks used in examples A-E and comparative examples F and G include the following: 2 or 4 centistoke (cSt) polyalphaolefin (PAO), a shear stable polyisobutylene, e.g. BP's Indopol™ H-300, and a high viscosity 150 cSt PAO, commercially available from ExxonMobil Chemical Company. TABLE 1 Compositions of Invention and Comparative Examples Comparative Examples Examples Commercial Oil A Oil B Oil C Oil D Oil E Oil F Oil G MTO Reference Synthetic AGO Additives in Basestocks*, wt % Extreme Pressure - High Presssure SIB 2.54 Extreme Pressure - High Presssure SIB 1.14 3.43 2.28 0.548 Extreme Pressure - High Presssure SIB 1.13 1.13 Antiwear - Mobilad C-421 - Acid Phosphate 0.238 0.738 1.476 0.703 0.690 0.112 0.818 Antiwear - Irgalube 349 - Aryl Phosphate 0.047 0.095 Dispersants - TEPA Succinimide + 0.593 0.180 0.360 0.893 1.010 0.143 1.19 Borated Version Rust Inhibitor - Primene 81R 0.147 0.672 0.492 0.88 0.427 0.141 0.506 Rust Inhibitor - Mobilad C-603 0.021 0.042 (Oxazolidone) Cobratec TT100 (Triazole Derivative) 0.0049 0.016 0.032 0.030 0.030 Alkylated Dimercaptothiadiazole - 0.0318 0.090 0.180 0.0795 0.0865 0.0127 0.103 Mobilad C-610 Other Additives (defoamants, antioxidants, balance balance balance balance balance balance balance etc.) Percentages and Ratios (mass %) in Oil: % S 0.513 0.564 0.531 1.538 1.035 0.246 1.29 % S/% Triazole Derivative 104 36 17 51 35 N/A N/A N/A N/A

The fluids in Table 1 were examined in the Eaton Copper Corrosion Test (TEP-247), which is a severe seven day corrosion test run at 150° C. This test is part of Eaton's PS-164 rev 7 specification for extended drain transmission fluids. The requirement is less than 5 mg of metal loss. The results for the compositions tested are shown in Table 2. The commercial MTO reference performs well in this test, but this is expected since the additive system is not based on S, P chemistry. The synthetic automotive gear oil, based on S, P chemistry, gives a result of 301 mg weight loss, which is more representative of S, P type chemistry in commercially available products. The examples F and G are further proof of the corrosion seen with S, P-based additive systems.

However, when lubricant compositions are designed within the scope of this invention, i.e. to include a triazole-containing derivative and thiadiazole-containing derivative, the corrosion is dramatically reduced to typically single digit amounts of metal loss due to corrosion. TABLE 2 Eaton Copper Corrosion Test (TEP 247) Weight Loss, mg* Examples A 1 B 3 D 10 E 8 Comparative F 181 G 100 Commercial MTO Reference 2 Synthetic AGO 301 *Requirement: 5 mg max

In Table 3, several of the lubricants in Table 1 were further evaluated in a screener test for the Eaton FZG Micropitting Test (TEP 272). The screener test (C-GF gear/8.3 ms⁻¹/120° C. controlled, splash lube) was developed to measure the amount of micropitting that occurred over the gear surface after load stages 7 (50 h), 8 (100 h), 9 (100 h) and 10 (50 h). This screener for the Eaton FZG Micropitting Test was run on Oils A and C and the results are contrasted in Table 3 to the reference MTO fluid. One sees that the compositions formulated according to this invention result in far less micropitting and wear on the gear surface relative to the MTO reference oil. TABLE 3 Screener for Eaton FZG Micropitting Test % Area Micropitted Wear, mg Examples A 42 57 C 17 35 Comparative Commercial MTO Reference 56.5 410

In Table 4, the results for ASTM D 5182 are shown. This test measures the scuffing load capacity of oils used to lubricate hardened steel gears. It mainly assesses the resistance to scuffing of mildly additized oils such as industrial gear oils, transmission oils, and hydraulic fluids. This test has also been incorporated into transmission specification requirements, but is likely to be replaced by a more severe EP load carrying test, e.g. FZG A10 gear/16.6 ms⁻¹ R/120° C. Heretofore, as far as the present inventors are aware, it has not been known how to achieve the combination of high load-carrying coupled with the meeting severe corrosion and micropitting requirements. Embodiments of the present invention solve this problem. TABLE 4 Evaluation of Scuffing Load Capacity with ASTM D 5182 Fail Load Stage* Examples A 12+ B 12+ D 12+ Comparative Commercial MTO Reference 7, 8 *Requirement: 8 or better

One of the advantages of embodiments of the present invention is the ability of S, P-based EP/antiwear agents to provide for an increase in the EP properties, while at the same time improving the micropitting and corrosion performance of the fluid. Without wishing to be bound by theory, the present inventors believe that the excellent performance seen in the extended Eaton Copper Corrosion Test is attributable in large part to the synergy obtained when both a triazole-containing derivative and a thiadiazole-containing derivative are present. The present inventors are unaware of other lubricant compositions containing S, P-based EP/antiwear additives that are able to meet these new requirements. The lubricant compositions of this invention also performed well in a micropitting test, which has become a desired feature of new transmission fluids.

The lubricant compositions of the present invention may be utilized, for example, in automotive transmissions, industrial gear boxes or in other applications where lubricants come into contact with copper or copper-containing alloys.

Trade names used herein are indicated by a ™ symbol or ® symbol, indicating that the names may be protected by certain trademark rights, e.g., they may be registered trademarks in various jurisdictions.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this invention and for all jurisdictions in which such incorporation is permitted.

When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those skilled in the art to which the invention pertains. Preferred embodiments of the invention include: (a) a lubricant composition suitable for use as a lubricating oil, said composition comprising at least one triazole-containing species and at least one thiadiazole-containing species; which may be further limited by one or more of the following limitations: said composition comprising at least one triazole-containing species and at least one species from the group consisting of dimercaptothiadiazole and alkylated derivatives thereof; said composition wherein the triazole-containing species is tolyltriazole; said composition further characterized by a ratio of thiadiazole-containing species to triazole-containing species of from about 20:1 to about 1:10, or more preferably about 10:1 to about 1:1; said composition further comprising at least one ingredient selected from (i) at least one sulfur-containing or boron-containing extreme pressure agent; and (ii) at least one phosphorus-containing antiwear agent; said composition further characterized by having a ratio of sulfur to triazole-containing species of less than about 150:1, or more preferably less than about 100:1; or said composition further comprising ingredients selected from extreme pressure agents, antiwear agents, dispersants, detergents, rust inhibitors, corrosion inhibitors, anti-foaming agents, demulsifiers, pour point depressants, seal swell agents, emulsifiers, tackifiers, antioxidants, VI improvers, thickening agents, and mixtures thereof; and (b) a lubricant composition according to any permutation given or fairly suggested by (a) and further comprising at least one basestock selected from API Groups I-V; and (c) an automotive transmission oil, industrial gear oil, hydraulic fluid, tractor oil comprising the lubricant composition of given or fairly suggested by (a) or (b); and (d) a manual transmission oil comprising and of the lubricant compositions given or fairly suggested by (a) or (b), which may also be further limited by embodiments wherein a basestock is included, said basestock selected from API Groups I-V and preferably selected from API Group IV, API Group V, and mixtures thereof, and still more preferably wherein said basestock composition is selected from API Group IV, and yet still more preferably wherein said basestock composition comprises 2 cSt and 150 cSt PAO or 4 cSt PAO and 150 cSt PAO, or any of the aforementioned compositions further comprising polyisobutylene; and (e) a lubricating fluid comprising a corrosion inhibitor, the improvement comprising the presence of an effective amount of a combination of a triazole-containing species and a thiadiazole-containing species (which embodiment may be further limited by any of the composition limitations given or fairly suggested by this paragraph); and (f) a vehicle comprising a manual transmission, said manual transmission lubricated by a composition according to any of the limitations given or fairly suggested by this paragraph; and (g) a transmission lubricated by any one of the compositions given or fairly suggested in this paragraph; and (h) a transmission lubricated by the lubricating fluids given or suggested in this paragraph; and (i) a method of preparing a lubricating composition comprising combining any of the compositions given or fairly suggested in (a) with at least one basestock selected from API Group I-V; and (j) a method of lubricating a transmission comprising adding any composition given or fairly suggested in this paragraph a transmission; and (k) a composition comprising at least one thiadiazole-containing species and at least one triazole-containing species in the ratio of about 20:1 to about 1:10, more preferably 10:1 to about 1:1, either compositions of which may further comprising at least one ingredient selected from (i) at least one sulfur-containing or boron-containing extreme pressure agent; and (ii) at least one phosphorus-containing antiwear agent, and (1) a fully formulated lubricant composition based on S, P chemistry comprising at least one thiadiazole-containing species and at least one triazole-containing species in the ratio of about 20:1 to about 1:10, preferably wherein said ratio is about 10:1 to about 1:1. As mentioned, any of these would immediately suggest to one of ordinary skill in the art in possession of the present disclosure numerous modifications. 

1. A lubricant composition suitable for use as a lubricating oil, said composition comprising at least one triazole-containing species and at least one thiadiazole-containing species.
 2. The composition of claim 1, comprising at least one triazole-containing species and at least one species from the group consisting of dimercaptothiadiazole and alkylated derivatives thereof.
 3. The composition of claim 1, where the triazole-containing species is tolyltriazole.
 4. The composition according to claim 1, further characterized by a ratio of thiadiazole-containing species to triazole-containing species of from about 20:1 to about 1:10.
 5. The composition according to claim 4, wherein the ratio of thiadiazole-containing species to triazole-containing species is from about 10:1 to about 1:1.
 6. The composition according to claim 1, further comprising at least one ingredient selected from (i) at least one sulfur-containing or boron-containing extreme pressure agent; and (ii) at least one phosphorus-containing antiwear agent.
 7. The composition according to claim 1, further characterized by having a ratio of sulfur to triazole-containing species of less than about 150:1.
 8. The composition of claim 1, further characterized by having a ratio of sulfur to triazole-containing species of less than about 100:1.
 9. The composition according to claim 1, further comprising ingredients selected from extreme pressure agents, antiwear agents, dispersants, detergents, rust inhibitors, corrosion inhibitors, anti-foaming agents, demulsifiers, pour point depressants, seal swell agents, emulsifiers, tackifiers, antioxidants, VI improvers, thickening agents, and mixtures thereof.
 10. A lubricant composition of claim 1 comprising at least one basestock selected from API Groups I-V.
 11. An automotive transmission oil, industrial oil, industrial gear oil, hydraulic fluid, tractor oil comprising the lubricant composition of claim
 1. 12. A manual transmission oil comprising the lubricant composition of claim
 1. 13. The manual transmission oil of claim 12, wherein said basestock comprises at least one basestock selected from API Groups I-V.
 14. The manual transmission oil of claim 12, wherein said basestock composition is selected from API Group IV, API Group V, and mixtures thereof.
 15. The manual transmission oil of claim 12, wherein said basestock composition is selected from API Group IV.
 16. The manual transmission oil of claim 12, wherein said basestock composition comprises 2 cSt and 150 cSt PAO.
 17. The manual transmission oil of claim 12, wherein said basestock composition comprises 4 cSt PAO and 150 cSt PAO.
 18. The manual transmission fluid of claim 12, further comprising polyisobutylene and one of: (a) a 2 cSt PAO and a 150 cSt PAO; or (b) a 4 cSt PAO and a 150 cSt PAO.
 19. In a lubricating fluid comprising a corrosion inhibitor, the improvement comprising the presence of an effective amount of a combination of a triazole-containing species and a thiadiazole-containing species.
 20. A vehicle comprising a manual transmission, said manual transmission lubricated by a composition according to claim
 11. 21. A transmission lubricated by the compositions of claim
 1. 22. A transmission lubricated by the lubricating fluid of claim
 19. 23. A method of preparing a lubricating composition comprising combining the composition of any one of claim 1 with at least one basestock selected from API Group I-V.
 24. A method of lubricating a transmission comprising adding a composition according to claim 23 to a transmission.
 25. A composition comprising at least one thiadiazole-containing species and at least one triazole-containing species in the ratio of about 20:1 to about 1:10.
 26. The composition according to claim 25, wherein said ratio is about 10:1 to about 1:1.
 27. The composition according to claim 1, further comprising at least one ingredient selected from (i) at least one sulfur-containing or boron-containing extreme pressure agent; and (ii) at least one phosphorus-containing antiwear agent.
 28. A fully formulated lubricant composition based on S, P chemistry comprising at least one thiadiazole-containing species and at least one triazole-containing species in the ratio of about 20:1 to about 1:10.
 29. The fully formulated lubricant composition of claim 28, wherein said ratio is about 10:1 to about 1:1. 